Maternal peptidoglycan overexposure during late pregnancy alters neurodevelopment and behavior in juvenile offspring

Emerging evidence suggests that maternal gut microbiota-derived metabolites and components influence fetal brain development and subsequent neurodevelopment. This study investigates the effects of maternal overexposure to muramyl dipeptide (MDP)-a bacterial peptidoglycan (PGN) motif recognized by Nod2 receptors-on offspring neurodevelopment and behavior. Time-mated C57BL/6J female mice received MDP via drinking water from gestational days 16-19. Nod2 activation in amniotic fluid was assessed using a Nod2 cell-based reporter assay, showing a significant increase in males 24 h after MDP exposure. Gene expression analysis revealed upregulation of PGN transporters in fetal brains, with males showing higher levels of Slc15a1/PepT1, Slc15a2/PepT2, and Slc46a2. No changes in inflammatory or microglia-related markers were found. Behavioral assessments during the juvenile period revealed sex-specific effects: prenatally exposed males showed reduced social interaction, while females exhibited reduced novelty-induced locomotion and impaired social recognition. These behavioral changes were linked to altered expression of synaptic (Dlg4, Ppp1r9b, Darpp-32) and microglial (Trem-2, Cx3cr1) genes in the prefrontal cortex. Our findings underscore the sex-specific effects of maternal PGN overexposure on offspring neurodevelopment, highlighting the potential role of the maternal microbiome in the neurobiology of neurodevelopmental disorders, even in the absence of infection or robust inflammation.